markjunk at mceahern.com
Thu Dec 27 17:21:33 CET 2001
> Perhaps then could someone explain to me how one compares classes
> useing the == operator, or indeed if this bad programming practice.
By overloading the __cmp__ method. Don't confuse the return value of
__cmp__ with whether or not the result of the comparison is that the two
instances being compared are equal. Examine this sample and note that
__cmp__ isn't merely used to determine equality. It is also used to
determine sort order.
def __init__(self, bar):
self.bar = bar
def __cmp__(self, other):
if self.bar == other.bar:
elif self.bar < other.bar:
return "<foo bar='%s'/>" % self.bar
a = foo(1)
b = foo(2)
c = foo(3)
d = foo(1)
list = [b, c, a]
print "before sorting:"
print "after sorting:"
print "a == d: %s" % (a == d)
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